The present invention relates to smoke containment curtains or smoke barriers, also known as curtain boards, used to contain smoke within a confined area, such as a ceiling segment or corridor, and especially to smoke containment curtains which emit only low quantities of toxic fumes when subjected to flame.
Fire safety has become a major issue following highly publicized fires during the 1980's in hotels, restaurants, prisons, on airlines and even on ships. These include the MGM Grand Hotel fire in Las Vegas where 85 people died, the Stouffer Hotel fire in Westchester, N.Y., where 26 victims lost their lives, and a cabin fire on an Air Canada flight in which 23 passengers perished. Many of these deaths were caused by toxic smoke and fumes, even though the victims were often far from the fire itself.
The chart below (reprinted from Progressive Architecture, September 1984 issue) lists the major toxicants in a fire, their most probable sources, and their effects on humans.
__________________________________________________________________________ GASES IDENTIFIED WITH COMBUSTION OF MATERIALS EXAMPLES OF TOXILOGICAL TOXICANTS SOURCE MATERIALS EFFECTS __________________________________________________________________________ Aldehydes Polyethylene Vapor Barriers, Polystyrene Insulation Potent respiratory (Arcolein, Acetaloehyde, (Hydrocarbons) irritants Furfural, etc.) Wood, Paper, Cardboard (Cellulosics) Urea-Formaldehyde Insulation (Urea-Formaldehyde Polymers) Polyurethane Foams in Furniture and Carpet Underlayment (Urethane Polymers) Polyester Fabrics and Fibers Ammonia Wool, Silk, Nylon, Polyurethane Foam, Melamine Pungent, unbearable Plastic Laminate (Nitrogen-containing material) odor; irritant to eyes and nose Carbon Dioxide Wood, Cotton, Paper (All Carbon-containing Increases respiration materials) Carbon Monoxide Wood, Cotton, Paper (All Carbon-containing Reduces Oxygen materials) carrying capacity of blood Halogen Acids Halon Fire-Retardants Respiratory irritants (Hydrobromic Acid, Halogenated Plastics and Fire-Retarded Natural and Hydrochloric Acid, Synthetic materials Hydrofluoric Acid) Polyvinyl Chloride Plastics Brominated Fire-Retarded Polyesters Hydrogen Cyanide Wool, Silk. Leather, Polyurethane Foam, Paper, A rapidly fatal Nylon, Urea-Formaldehyde Insulation, asphyxiant poison, Polyacrylonitrile (Nitrogen-containing materials) reduces normal cell metabolism Hydrogen Chloride Polyvinyl chloride plastics Respiratory irritant; Some Fire-Retardant treated materials potential toxicity of HCI coated on particulate may be greater than that for an equivalent amount of gaseous HCI Isocyanates Polyurethane Foam (Urethane Polymers) Potent respiratory irritants; believed the major irritants in smoke of Isocyanate- based urethanes Nitrogen Oxides Wood, Nylon, Cellulose, Polyurethane Foam Strong pulmonary (Nitrogen-containing materials) irritant capable of causing immediate death as well as delayed injury Hydrogen Sulfide Sulfur Polysulfides, Sulfur-crosslinked natural and A strong irritant, Dioxide rubber (Sulfur-containing materials) intolerable well below lethal concentrations __________________________________________________________________________
While experts may disagree on the relative toxicity of these various combustion gases, all agree, however, that the less smoke and fumes that are given off in a fire, the better the chance the victims have of surviving the fire.
Various state and federal regulations have been passed to address this concern. For example, every end product used in the construction of public buildings in New York State must be tested and registered for toxicity according to the University of Pittsburgh protocol. The North Carolina Building Code requires the installation of curtain boards in the ceiling of buildings having a floor area in excess of 10,000 square feet in a single expanse. Basically, these curtain boards descend downwardly four to six feet from the ceiling, forming a gridwork of rectangular cells which join other cells dividing the ceiling into zones of, e.g., about 2,000 square feet. During a fire, smoke rising toward the ceiling is collected in the cells and prevented by the curtain boards from spreading. Exhaust fans in the ceiling above the cells can then remove the smoke from the building.
Historically, smoke curtain boards were formed of metal or dry wall panels which were unwieldy to handle and required a complex supporting framework and installation procedure. A structure overcoming these disadvantages is described in U.S. Pat. No. 5,240,058 to Ward. In the Ward structure, the metal or dry wall boards are replaced by a resin-coated fiberglass fabric with attachment devices such as longitudinal hems sewn into the fabric, which allow the fabric to be supported on a framework of metal pipes. Other flexible products including flame retardant cotton or synthetic fabrics, vinyl films, and laminated or coated materials would probably meet the need for a non-porous, flame retardant, and drapable curtain board material, but these organic based products would quickly lose their structure and shape in a fire scenario and allow the smoke to spread through the building. A suitable fabric is said to be Sandel.RTM. fabric (available from Firesafe Products, 276 5th Ave., Suite 300, New York, N.Y. 10001) weighing 8.6 ounces per square yard maximum weight, which is flame retardant anal has d 0.0 CFM air permeability.
Sandel.RTM. fabric, originally developed as a mattress ticking, has a structure like the fabric described in U.S. Pat. No. 4,526,830 to Ferziger, and is comprised of a woven fiberglass fabric coated with a polymeric carrier containing a fire retardant. The carrier is a halide-containing resin, such as an acrylic vinyl chloride latex. Suitable fire retardants include aluminum trihydrate, antimony trioxide and antimony pentaoxide. Other ingredients, such as fungicides and bactericides can be added to the coating.
Various other fabrics comprised of a fiberglass substrate fabric and a polymeric coating have been described in the prior art. The properties of these fabrics differ depending on their end use. U.S. Pat. No. 4,677,016 to Ferziger, for example, describes a fabric impermeable to light suitable as a black out curtain or shade, which is comprised of a tightly woven fiberglass fabric substrate coated on at least one surface with an opaque foam coating comprised of a cured layer of flame retardant polymeric latex foam carrier containing a fire retardant. The preferred carrier for these fabrics is also a halide-containing polymer, preferably acrylic vinyl chloride latex. Fire retardants include antimony trioxide and/or antimony pentaoxide, and aluminum trihydrate, which also acts as a filler. A black pigment is added to increase the opacity of the fabric.
U.S. Pat. No. 4,695,507 to Schwartz describes ceiling board facing fabric useful in providing a decorative acoustical surface to ceilings and walls, which has a nubby architectural appearance. The fabric eliminates the spray painting normally required to achieve the three-dimensional nubby appearance. The fabric is comprised of a woven, knitted or non-woven fiberglass substrate fabric formed with textured fill yarns. The fabric is coated with a coating or finish which is essentially free of halogen groups (chlorides, bromides, fluorides), nitrile, nitrate, amine, sulfate, phosphate, and other potentially offending chemical groups which can emit toxic fumes if burned. The finish is preferably an acrylic or silicone resin which contains a non-toxic flame retardant such as aluminum hydrate, and a white pigment. A porous fabric, which is necessary to achieve the desired acoustical properties, is obtained by 1) using an open fabric and then padding the fabric with the low viscosity coating, or 2) knife coating a frothed composition onto the fabric.
U.S. Pat. No. 4,778,544 to Jones et al describes a fabric useful as a facing for Navy board, or hull board, used to form walls and partitions on board ships, and for similar uses. This fabric, which must be rigid, slittable and paintable, is formed by coating a tightly woven fiberglass fabric with a halide-free finish comprised of an acrylic or silicone resin containing a flame retardant and a white pigment.
While the above and other coated fiberglass fabrics have been described in the prior art, some of the fabrics previously disclosed are not suitable for use as a smoke containment curtain or "curtain board" in a structure such as that described in the Ward patent because the fabrics may be too porous or not drapable enough. The products described in the Ferziger patents may be non-porous and drapable, but the halogen finishes can give off toxic hydrochloric acid fumes when heated or burned. Ideally, fabrics for smoke containment curtains should have flexibility and tear resistance, yet should be readily cut and shaped during installation. Such fabrics should be smoke impermeable and, very importantly, should release at most only small amounts of relatively non-toxic fumes when exposed to heat or flame. A fabric having these characteristics would be of great utility in the construction of curtain boards of the type described above, as well as in other barriers to prevent the movement of smoke.